Field of the Invention
The invention relates to a radar level gauge comprising a safety device.
Background of the Invention
Radar level gauges with safety devices are known from prior art, for example from U.S. Pat. No. 8,009,085 B2, and show a signal generator for generating electromagnetic waves and an antenna for emitting the electromagnetic waves into a container as well as for receiving reflected electromagnetic waves from the container, with the safety device being embodied suitable to check the functionality of the radar level gauge. The safety devices shown in prior art comprise for this purpose a reflector and an adjustment device, which are embodied suitable to adjust the reflector at least between a first position in which it reflects the electromagnetic waves and a second position in which it reflects the electromagnetic waves in a reduced fashion.
The radar level gauges known from prior art are generally used in containers, usually tanks or silos, which are embodied for storing various materials. For example food, drinks, drugs, or fuels are stored in such tanks or silos, so that a touchless fill level measurement is required. In prior art, for example the above-mentioned radar level gauges or alternatively ultrasound-based fill level gauges are known as touchless fill level measuring technologies. Based on their high precision of measurement and their low susceptibility to malfunction here radar level gauges are widely used.
The radar level gauges known from prior art are generally fastened via a flange in the upper area of the tank or silo, with an electronic being arranged outside the housing and an antenna of the radar level gauge being arranged inside thereof. The antenna is aligned in a suitable fashion so that electromagnetic waves, i.e. particularly a radar signal, can be sent in the direction towards the filled in material stored inside the container, and that it can receive electromagnetic waves reflected by said material. Based on a time difference between emitting the electromagnetic signal and receiving the reflected electromagnetic signal here a fill level inside the container can be determined. Potential measuring systems are here the pulse-radar system, in which radar pulses are emitted in the direction of the goods to be measured, are reflected there, and a fill level determination then occurs by determining the traveling time, as well as the frequency-modulated continuous wave method, in which a frequency-modulated high-frequency signal is emitted with increasing frequency and the fill level is then determined from the frequency difference between emitted and received signals.
For the functional control of a radar level gauge, particularly to test its functionality in a safety-relevant maximum fill level, a fill level at which an automatic protection system prevents any further filling in and perhaps at other relevant fill levels, it is necessary to provide a safety device, which allows a statement regarding the functionality at said maximum fill level. For this purpose, it is known in prior art during a safety test to move a reflector manually into the radiation path of the radar level gauge in order to test here, even in case of lower fill levels of the container, to check the function of the level gauge at a desired fill level by inserting the reflector at this fill level into the radiation path of the radar level gauge and this way to generate a reflection at the desired fill level.
In safety-relevant measuring applications it is common to provide additional sensors for detecting a fill level or limit in order to generate redundancy. Further it is common to monitor respective tanks additional for their temperature and/or pressure. In applications known from prior art here it is considered disadvantageous that in addition to the already provided radar level gauge with an integrated safety device, more assembly options must be provided for other sensors and tanks. This is considered particularly disadvantageous in that here the additional assembly opening, for example for a flange, increases the susceptibility for malfunctions of the entire system, for example with regards to tight seals.
Therefore, the objective of the present invention is to further develop a radar level gauge known from prior art and provided with a safety device such that the disadvantages known from prior art are avoided.